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Just wondering if anyone can enlighten me as to why they make white LEDs reverse polarity to standard LEDs? I can't think of any reason other than to make it awkward for the hobbist. I mean where's the logic in it? Also why not make CBE in transistors standard and while they are at it make the 78XX regulators have the same pinouts for the 100ma and 1A units
Ahhh feels much better now I have that out my monday morning rant.
The universal answer is... BECAUSE! ;)
Why do cars not have a standard layout for the controls.
My two cars have the indicator stalks and windshield wiper stalks the opposite way round. When I use the wifes car I usually wipe the windshield instead of signalling my intention to turn !!!!
Thankfully there does seem to be a standard layout to the foot controls !!!!
But I do understand your frustration.
Was looking at some RGB LEDS on a website today and the pinout was differnet for Common Anode and Common Cathode.
Green
Blue
CommonCathode
Red
Green
Blue
Red
CommonAnode
That's a very good point. It's not like they couldn't standardize pin configurations. The actual chip is usually no bigger than the size of a head on a matchstick. (Freaky) Case size is normally dominated by the number of pins required. I guess also to, to some extent - thermal dissipation can denote size.Quote:
Originally Posted by George
But some devices, particularly transistors are available in several pinouts for what is electrically the same device.Quote:
Originally Posted by T.Jackson
BC182/BC182L (NPN) and its complimentary device BC212/BC212L (PNP) are in TO92 packages but with different pinouts.
The non "L" version is TO92-4 EBC
The "L" version is TO92-1 BCE
Thinking about it a bit more....
Why are 78xx regulators IN-GND-OUT whereas 79xx regulators are GND-IN-OUT
Apart from possible intentions of helping to simplify PCB layout - it all makes no sense.
well, if the tab was GND, then it would simplify the board layout. I'm guessing more about an internal structure rather than this... but everyone may have it's own assumption... only the original designer would probably know...
thinking about reference in a dual rail supply... you could discover why they do it like that... is 79xxx really a 79xx or a 78xxx relabelled ??? i didn't compare their internal schematic.
if everything would be standard, it would remove all fun...
I don't think the internals force restrictions on anything. It's about the size of a head on a matchstick in most cases. But hey, I don't work in Silicon Valley, so I place no bets on anything.
Believe it or not, this same complaint surfaced many years before transistors and integrated circuits!
The issue (this was back when the Earth's crust was still cooling) was why can't the same kinds of vacuum tubes (i.e., diode, dual diode, triode, etc.) have the same pinout?
In those days (there was no Silicon Valley and you could still afford to buy a house in California), the issue had to do, always first and foremost, with both the electrical characteristics of the device and good engineering practice.
And, in the end, the same thing occurred--two vacuum tubes, identical or nearly so, would have different pinouts.